Forming conductive vias using a light guide

ABSTRACT

The present invention provides a process and a structure of forming conductive vias using a light guide. In an exemplary embodiment, the process includes providing a via in a base material in a direction perpendicular to a plane of the base material, applying a photoresist layer to an interior surface of the via, inserting a light guide into the via, exposing, by the light guide, a portion of the photoresist layer to light, thereby resulting in an exposed portion of the photoresist layer and an unexposed portion of the photoresist layer, removing a portion of the photoresist layer, and plating an area of the via, where the photoresist has been removed, with a metal, thereby resulting in a portion of the via plated with metal and a portion of the via not plated with metal.

BACKGROUND

The present disclosure relates to conductive vias in printed circuitboards, and more specifically, to forming conductive vias using a lightguide.

SUMMARY

The present invention provides a process and a structure of formingconductive vias using a light guide. In an exemplary embodiment, theprocess includes providing a via in a base material in a directionperpendicular to a plane of the base material, applying a photoresistlayer to an interior surface of the via, inserting a light guide intothe via, exposing, by the light guide, a portion of the photoresistlayer to light, thereby resulting in an exposed portion of thephotoresist layer and an unexposed portion of the photoresist layer,removing a portion of the photoresist layer, and plating an area of thevia, where the photoresist has been removed, with a metal, therebyresulting in a portion of the via plated with metal and a portion of thevia not plated with metal.

In an exemplary embodiment, the process includes providing a via in abase material, including at least two copper lines and at least oneinsulator layer separating the at least two copper lines, in a directionperpendicular to a plane of the base material, where the via intersectsthe at least two copper lines, applying a photoresist layer to aninterior surface of the via, inserting a light guide into the via, wherea portion of an outer surface of the light guide is masked, exposing,via the light guide, a portion of the photoresist layer to light,thereby resulting in an exposed portion of the photoresist layer and anunexposed portion of the photoresist layer, removing a portion of thephotoresist layer, and plating an area of the via, where the photoresisthas been removed, with a metal, thereby resulting in a portion of thevia plated with metal and a portion of the via not plated with metal.

In an exemplary embodiment, the process includes providing a via in abase material, including at least two copper lines and at least oneinsulator layer separating the at least two copper lines, in a directionperpendicular to a plane of the base material, where the via intersectsthe at least two copper lines, applying a photoresist layer to aninterior surface of the via, inserting a light guide into the via,exposing, via the light guide, a portion of the photoresist layer tolight, thereby resulting in an exposed portion of the photoresist layerand an unexposed portion of the photoresist layer, removing a portion ofthe photoresist layer, and plating an area of the via, where thephotoresist has been removed, with a metal, thereby resulting in aportion of the via plated with metal and a portion of the via not platedwith metal.

In an exemplary embodiment, the structure includes a light source, alight guide, attached to the light source, where the light guide iscapable of transmitting light from the light source, and a mask at aportion of a surface of the light guide, thereby resulting in anuncovered portion of the light guide and a covered portion of the lightguide, where at least a portion of the light guide is designed such thatit may be inserted into a via of a printed circuit board.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a diagram in accordance with an exemplary embodiment ofthe present invention.

FIG. 2A depicts a cutaway diagram in accordance with an exemplaryembodiment of the present invention.

FIG. 2B depicts a cutaway diagram in accordance with an exemplaryembodiment of the present invention.

FIG. 2C depicts a cutaway diagram in accordance with an exemplaryembodiment of the present invention.

FIG. 2D depicts a cutaway diagram in accordance with an exemplaryembodiment of the present invention.

FIG. 2E depicts a cutaway diagram in accordance with an exemplaryembodiment of the present invention.

FIG. 2F depicts a cutaway diagram in accordance with an exemplaryembodiment of the present invention.

FIG. 3A depicts a cutaway diagram in accordance with an exemplaryembodiment of the present invention.

FIG. 3B depicts a cutaway diagram in accordance with an exemplaryembodiment of the present invention.

FIG. 3C depicts a cutaway diagram in accordance with an exemplaryembodiment of the present invention.

FIG. 3D depicts a cutaway diagram in accordance with an exemplaryembodiment of the present invention.

FIG. 3E depicts a cutaway diagram in accordance with an exemplaryembodiment of the present invention.

FIG. 3F depicts a cutaway diagram in accordance with an exemplaryembodiment of the present invention.

FIG. 4 depicts a diagram in accordance with an exemplary embodiment ofthe present invention.

FIG. 5 depicts a diagram in accordance with an exemplary embodiment ofthe present invention.

FIG. 6 depicts a diagram in accordance with an exemplary embodiment ofthe present invention.

FIG. 7 depicts a diagram in accordance with an exemplary embodiment ofthe present invention.

FIG. 8 depicts a cutaway diagram in accordance with an exemplaryembodiment of the present invention.

FIG. 9 depicts a diagram in accordance with an exemplary embodiment ofthe present invention.

FIG. 10 depicts a cutaway diagram in accordance with an exemplaryembodiment of the present invention.

FIG. 11 depicts a diagram in accordance with an exemplary embodiment ofthe present invention.

FIG. 12 depicts a flowchart in accordance with an exemplary embodimentof the present invention.

DETAILED DESCRIPTION

The present invention provides a process and a structure. In anexemplary embodiment, the process includes providing a via in a basematerial in a direction perpendicular to a plane of the base material,applying a photoresist layer to an interior surface of the via,inserting a light guide into the via, exposing, by the light guide, aportion of the photoresist layer to light, thereby resulting in anexposed portion of the photoresist layer and an unexposed portion of thephotoresist layer, removing a portion of the photoresist layer, andplating an area of the via, where the photoresist has been removed, witha metal, thereby resulting in a portion of the via plated with metal anda portion of the via not plated with metal.

In an exemplary embodiment, the process includes providing a via in abase material, including at least two copper lines and at least oneinsulator layer separating the at least two copper lines, in a directionperpendicular to a plane of the base material, where the via intersectsthe at least two copper lines, applying a photoresist layer to aninterior surface of the via, inserting a light guide into the via, wherea portion of an outer surface of the light guide is masked, exposing,via the light guide, a portion of the photoresist layer to light,thereby resulting in an exposed portion of the photoresist layer and anunexposed portion of the photoresist layer, removing a portion of thephotoresist layer, and plating an area of the via, where the photoresisthas been removed, with a metal, thereby resulting in a portion of thevia plated with metal and a portion of the via not plated with metal.

In an exemplary embodiment, the process includes providing a via in abase material, including at least two copper lines and at least oneinsulator layer separating the at least two copper lines, in a directionperpendicular to a plane of the base material, where the via intersectsthe at least two copper lines, applying a photoresist layer to aninterior surface of the via, inserting a light guide into the via,exposing, via the light guide, a portion of the photoresist layer tolight, thereby resulting in an exposed portion of the photoresist layerand an unexposed portion of the photoresist layer, removing a portion ofthe photoresist layer, and plating an area of the via, where thephotoresist has been removed, with a metal, thereby resulting in aportion of the via plated with metal and a portion of the via not platedwith metal.

In an exemplary embodiment, the structure includes a light source, alight guide, attached to the light source, where the light guide iscapable of transmitting light from the light source, and a mask at aportion of a surface of the light guide, thereby resulting in anuncovered portion of the light guide and a covered portion of the lightguide, where at least a portion of the light guide is designed such thatit may be inserted into a via of a printed circuit board.

One of the major signal performance concerns of current and nextgeneration multi-layer printed circuit boards (PCB) is degradation ofelectrical signals traveling through vias between layers due to stubs. Amulti-layer PCB is a stack of PCB cards, with electrical components oneach of the PCB cards. One method of connecting the layers of the PCBcards is by forming vias (or holes) through one or more of the PCBlayers and coating or depositing metal on the inner surface of the via.A stub is the undesired portion of a coated via in a multi-layer beyondthe desired portion of the coated via. In the design of large computersystems, PCB with a significant number of signal layers are possible.Metal coated vias are used in multi-layered printed circuit boards toelectrically connect conductive lines or traces in differing layers ofthe printed circuit boards. Multiple metal coated vias may be requiredto form a connection of internal wiring between mounted circuit devicesor connections to other interfaces such as I/O connectors.

During the manufacturing of the printed circuit board, the vias may becreated by plating drilled vias in the board with a conductive material(e.g., copper). Typically, the entire depth of the via may be platedwith the copper material. In this context, a stub refers to a portion ofthe via extending beyond the desired signal layer escape, and hence notpart of the main-line signal path.

In order to reduce the impact of stubs on circuit board performance, thestubs may be removed from the board, or at least shortened, during themanufacturing process. One method for removing stubs is called backdrilling. In this process, a drill bit, commonly one which has aslightly larger diameter than the bit used in predrilling the hole forthe via (prior to plating), may be used by a drill for boring into thevia and removing the plating material from its stub portion.

In an embodiment, a multilayer PCB is formed with a via (e.g., throughhole) through two or more layers of the PCB. In an embodiment, the viais formed by drilling or punching a hole through the PCB after themultilayer PCB is stacked. In an embodiment, the via is formed byaligning individual holes in in the PCB layers to form a single via. Inan embodiment, the via runs through the full thickness of the PCB. Forexample, a via could be drilled through each of the layers after the PCBis formed. In an embodiment, the via runs through some of the layers butnot all of the layers of the PCB. For example, vias could be punchedthrough a portion of the layers of the PCB and those portions could bealigned during assembly of the multilayer PCB. In an embodiment, the PCBhas multiple through holes or vias similar to the aforementioned vias.

In an embodiment, after formation of the via in the PCB, the via will becoated with a photoresist resin resulting in a photoresist layer on theinner surface of the via. In an embodiment, the photo resin is apositive photoresist. In a positive photoresist resin, the portion ofthe photoresist that is exposed to light becomes soluble to aphotoresist developer while the unexposed portion of the photoresistresin remain insoluble to the photoresist developer.

In an embodiment, the photoresist resin is a negative photoresist resin.In a negative photoresist resin the portion of the photoresist that isexposed to light becomes insoluble to the photoresist developer whilethe unexposed portion of the photoresist is dissolved by the photoresistdeveloper. In an embodiment, the photoresist is a photopolymericphotoresist. For example, the photoresist could be methyl methacrylate.In an embodiment, the photoresist is a photodecompostable photoresist.For example, the photoresist could be diazonaphtaquinone. In anembodiment, the photoresist is a photo crosslinking photoresist. In anembodiment, the photoresist is a self-assembled monolayer photoresist.In an embodiment, air is blown into the via after coating with thephotoresist to prevent tenting. Tenting is a meniscus layer of thephotoresist resin on the surface of the via.

In an embodiment, a light guide is inserted into the via. The lightguide is capable of transmitting light from a light source and exposinga portion of the via with the light from the light source. In anembodiment, the light guide could be any optical cable or projectingmember that is capable of transmitting light.

In an embodiment, a portion of an outer surface of the light guide ismasked. In an embodiment, the mask is designed to prevent light fromexiting the light guide in the portion of the light guide where theouter surface is covered by the mask. In an embodiment, the mask isdesigned to reflect or refract light back in towards the light guide inthe portion of the light guide where the outer surface covered is by themask. In an embodiment, the masked portion of the light guide has two ormore masked regions separated by one or more unmasked regions. In anembodiment, the mask is a coating on the surface of the light guide. Inan embodiment, the light guide would be masked by a surface treatmentthat is reflective of the wave length of light that is being used in thephoto resistive process. For example, silver nitrate could be used. Inan embodiment, the mask absorbs light. For example, an optical blackcoating could be used to absorb light.

In an embodiment, the light guide is tuned to optimize the light guidestransmission of the light. For example, stress or strain can be inducedin the light guide to change the optical properties of the light guide.In an embodiment, the mask is a treatment of the surface of the lightguide. For example, the mask could be an etching of the surface of thelight guide. The mask could also combine an etching with a coating. Inan embodiment, the unmasked region is etched to affect lightdissemination to the surface of the via. In an example, the light guideis a transparent core surrounded by a transparent cladding material witha lower index of refraction where the transparent cladding material witha lower index of refraction is the mask. In an embodiment, thetransparent cladding only partially covers the surface of the lightguide. In an embodiment, the light guide is not masked. In anembodiment, the end of the light guide is masked.

In an embodiment, the light guide is a fiber optic element. In anembodiment, the light guide has light dispersion characteristics suchthat light will come out of the sidewall of the light guide. In anembodiment, the light guide is designed such that light will come out ofthe end of the light guide. In the embodiment, the light guide isdesigned such that the light has a multi-mode dispersion at thesidewalls. In an embodiment, the end of the light guide is cleft or cutoff, such that the light is dispersed towards the sidewalls of the viait is inserted into. For example, the light guide could be cut offstraight or rounded with multiple cutes. The light guide could also haveother modifications done to the end of the light guide to affect the waylight is dispersed out of the light guide.

In an embodiment, the end of the light guide is designed according tothe desired light transmission profile. For example, the end of thelight guide could be cleft off straight, formed with a rounded end, orformed with a tapered side. In an embodiment, the end of the light guidehas an optical coating. In an embodiment, any portion of the light guidethat is not masked will have an optical coating. An optical coating is acoating that affects the way light is transmitted/dispersed out of orreflected/refracted back into the light guide.

In an embodiment, the light guide is connected to a light source (e.g.,an LED, a lightbulb, the sun, etc.). The source can be any light sourcecapable of introducing light (e.g., visible, ultraviolet, infrared,etc.) into the light guide for transmission to the intended surfaces. Inan embodiment, the light guide is a light source.

In an embodiment, a photoresist layer is a positive tone photoresistmaterial. In an embodiment, the removing includes removing the exposedportion of the photoresist layer. In an embodiment, the photoresistlayer is a negative tone photoresist material. In an embodiment, theremoving includes removing an unexposed portion of the photoresistlayer. In an embodiment, the removing includes washing the via with aphotoresist developer. In an embodiment, a photoresist developer is aliquid that dissolves uncured resin in a negative tone photoresist. Inan embodiment, a photoresist developer is a liquid that dissolves curedresin in a positive tone photoresist. After washing the via will be leftwith a portion of the via having a bare surface and a portion of the viahaving a surface coated with photoresist.

In an embodiment, copper is deposited on the bare surface of the via. Inan embodiment, a thin seed layer is deposited on the bare surface of thevia followed by a thicker metal layer. In an embodiment, the metaldeposited is any conductive metal (e.g., copper or gold).

Referring to FIG. 1, in an embodiment, a multilayer PCB 100 is formedwith a via 130 a first line 120 on a first layer of base material 110and a second line 125 on a second layer of base material 110. In oneembodiment, base material 110 is an insulating material. For example,base material 110 could include oxide materials, silicon materials, orfiberglass materials. In an embodiment, in order to form a connectionbetween first line 120 and second line 125 in via 130, without a stubextending significantly beyond the intended coverage, a light guide isused to selectively cure a photoresist on the inner surface of via 130.

Positive Tone Photoresist Process

Referring to FIG. 2A, in an embodiment, a process for producing a PCBpackage 200 includes providing a via 230 in a base material 210 in adirection perpendicular to a plane of base material 210, metal lines 220on top of layer 250 and metal line 225 on top of layer 253. Layers 250,251, and 252 separate metal lines 220 and 225.

Referring to FIG. 2B, a photoresist layer 236 is applied to an interiorsurface of via 230.

Referring to FIG. 2C, the process further includes inserting a lightguide 270 into via 230, and exposing, by light guide 270, a portion ofthe photoresist layer to light. In an embodiment, a portion of an outersurface of light guide 270 is masked, resulting in a masked portion 275and an unmasked portion 276 of light guide 270.

Referring to FIG. 2D, exposing the portion of the photoresist layer tolight, thereby results in an exposed portion 280 of the photoresistlayer and an unexposed portion 261 of the photoresist layer. Unmaskedportion 276 of light guide 270 is designed to expose only a portion ofvia 230 that is intended to be exposed, resulting in exposed portion280. In and embodiment, the tip of light guide 270 is designed to focuslight only to intended layers, thereby not curing additional layers. Inan embodiment, unexposed portion 261 is left uncured so a washing doesnot remove the photoresist. In a positive tone photoresist, thedeveloper used in washing removes the cured/exposed photoresist. Thus,metal will not be deposited on the surface of via 230 where photoresistremains.

Referring to FIG. 2E, in an embodiment using a positive tone photoresistmaterial, a washing process removes exposed portion 280 of photoresistlayer 236. In an embodiment, metal is deposited or plated an area 235 ofvia 230, where the photoresist has been removed.

Referring to FIG. 2F, in an embodiment, metal is deposited or plated anarea 235 of via 230, where the photoresist has been removed, therebyresulting in a portion of via 230 with metalized region 290 and anunexposed portion 261 of via 230 without metal. In an embodiment, layers250, 251, and 252 have metal deposited in the portion of via 230 runningthrough layers 250, 251, and 252 forming metalized region 290 thatconnects metal line 220 to metal line 225. In an embodiment, in order toensure metal line 220 connects to metal line 225, the portion of via 230in layer 253 may be partially plated with metal extending from metalizedregion 290 partially down into layer 253. For example, the portion ofvia 230 in layer 253 could be partially exposed by light guide 270 suchthat, after washing and depositing, layer 253 has enough metal platingto ensure coverage of metal line 225, but not enough metal to contact aline between layers 253 and 254. In an embodiment, this processeliminates or reduces the formation of a stub in unexposed portion 261of via 230.

Negative Tone Photoresist Process

Referring to FIG. 3A, in an embodiment, a process for producing a PCBpackage 300 includes providing a via 330 in a base material 310 in adirection perpendicular to a plane of base material 310, metal lines 320on top of layer 350 and metal line 325 on top of layer 353. Layers 350,351, and 352 separate metal lines 320 and 325.

Referring to FIG. 3B, a photoresist layer 336 is applied to an interiorsurface of via 330.

Referring to FIG. 3C, the process further includes inserting a lightguide 370 into via 330, and exposing, by light guide 370, a portion ofthe photoresist layer to light. In an embodiment, a portion of an outersurface of light guide 370 is masked, resulting in a masked portion 375and an unmasked portion 376 of light guide 370.

Referring to FIG. 3D, in an embodiment, exposing, by light guide 370, aportion of the photoresist layer to light, thereby resulting in anexposed portion 380 of the photoresist layer and an unexposed portion361 of the photoresist layer. Unmasked portion 376, of light guide 370,is designed to expose only exposed portion 380 of via 330 that isintended to be exposed. In and embodiment, the tip of light guide 370 isdesigned to focus light only to intended layers, thereby not curingadditional layers.

Referring to FIG. 3E, in an embodiment using a negative tone photoresistmaterial, a washing process removes unexposed portion 361 of thephotoresist. In a negative tone photoresist process, washing the viawith a photo developer will remove unexposed/uncured photoresist resin.In an embodiment, an exposed portion 380 is cured so a washing does notremove the photoresist. Thus, metal will not be deposited on the surfaceof via 330 where photoresist remains. In an embodiment, metal isdeposited or plated an area 385 of via 330, where the photoresist hasbeen removed, thereby resulting in a portion of via 330 with metalizedregion 390 and an exposed portion 380 of via 330 without metal.

Referring to FIG. 3F, in an embodiment, metal is deposited or plated anarea 385 of via 330, where the photoresist has been removed, therebyresulting in a portion of via 330 with metalized region 390 and anexposed portion 380 of via 330 without metal. In an embodiment, layers350, 351, and 352 have metal deposited in via 330 forming metalizedregion 390 that connects metal line 320 to metal line 325. In anembodiment, in order to ensure metal line 320 connects to metal line325, layer 353 via may be partially plated with metal, extendingmetalized region 390 partially down into layer 353. For example, layer353 could be only partially exposed by light guide 370 such that, afterwashing and depositing, layer 353 has enough metal playing to ensurecoverage of metal line 325, but not enough metal to contact a linebetween layers 353 and 354. In an embodiment, this process eliminates orreduces the formation of a stub in exposed portion 380.

Light Guide

Referring to FIG. 4, in an embodiment, a light guide is part of astructure including a light source 405, a light guide, attached to lightsource 405, where the light guide is capable of transmitting light fromlight source 405, and a mask region on a portion of the surface of thelight guide, thereby resulting in an uncovered region 476 of the lightguide and masked region 475 of the light guide, where the light guide isdesigned such that it may be inserted into a via in a printed circuitboard.

In an embodiment, masked region 475 is the area running from lightsource 405 to an uncovered region 476. Thus, light will only be emittedfrom uncovered region 476. The line between masked region 475 anduncovered region 476 will correspond to the limit of light exposure onthe via wall. Likewise, the end of the light guide will only cure thesurface of the via near the exposed end.

Referring to FIG. 5, in an embodiment, a light guide is part of astructure including a light source 505, a light guide, attached to lightsource 505, where the light guide is capable of transmitting light fromlight source 505, and a mask region on a portion of the surface of thelight guide, thereby resulting in an uncovered portion 575 of the lightguide and masked region 576 of the light guide, where the light guide isdesigned such that it may be inserted into a via in a printed circuitboard.

In an embodiment, uncovered region 575 will run to masked region 576.Light will be emitted from uncovered region 575, and light will not beemitted from masked region 576. The line between uncovered region 575and masked region 576 will correspond to a region of the via between thecured region and the uncured region.

Referring to FIG. 6, in an embodiment, a light guide has multiple maskedand exposed regions. Uncovered regions 676 and 678 would curecorresponding regions of the photoresist on the surface of a via(similar to exposed portion 280 and exposed portion 380), and maskedregions 675 and 677 would prevent curing of areas of the via (similar tounexposed portion 261 and unexposed portion 361).

Referring to FIG. 7, in an embodiment, a light guide has multiple maskedand exposed regions. Uncovered regions 776 and 778 would curecorresponding regions of the photoresist on the surface of a via, andmasked regions 775 and 777 would prevent curing of areas of the via.

Referring to FIG. 8 and FIG. 9, in an embodiment, a light guide ismasked in several areas to form intermittent conductive regions in a via830. For example, using a light guide, such as light guide 900, withmultiple masked regions, multiple conductive regions of a via could beformed. An exposure from light guide 900 on via 830 on a negative tonephotoresist would result in regions 861 and 862 being exposed and/orcured. Washing would subsequently remove unexposed/uncured photoresistresin from regions 890, 891, and 892. Metal deposition or plating of via830 would result in regions 890, 891, and 892 being coated with metal,resulting in a conductive connection between metal lines 820 and 821,between metal lines 822 and 823, and between metal lines 824 and 825. Inan embodiment, regions 861 and 862 are designed to be slightly smallerthan depicted to ensure that the metal coating in regions 890, 891, and892 cover metal lines 820, 821, 822, and 823. Exposed region 976corresponds to region 861 of the remaining photoresist coating, andexposed region 978 corresponds to region 862 of the remainingphotoresist resin.

Referring to FIG. 10 and FIG. 11, in an embodiment, two or more lightguides with one or more exposed regions could be inserted from oppositeends of a via 1030 to expose photoresist resin on the surface of via1030. For example, light guide 1100 could be inserted from the top ofvia 1030 and light guide 1101 could be inserted from the bottom of via1030. Using a positive tone photoresist, exposed regions 1176 and 1178would cure resin in via 1030 regions 1090 and 1091. Likewise, exposedregion 1174 on light guide 1101 would expose region 1092 of via 1030.The cured positive tone photoresist in regions 1090, 1091, and 1092could be washed away. Metal could then be formed on exposed surfaces inregions 1090, 1091, and 1092. In an embodiment, cured regions 1090,1091, and 1092 could be over exposed, by reducing masked regions 1175,1177, and 1173, to ensure that metal lines 1020, 1021, 1022, 1023, 1024,and 1025 are electrically connected to the respective conductive regions1090, 1091, and 1092.

Referring to FIG. 12, in an exemplary embodiment, the present inventionis configured to perform an operation 1210 of providing a via in a basematerial in a direction perpendicular to a plane of the base material,operation 1220 of applying a photoresist layer to an interior surface ofthe via, operation 1230 of inserting a light guide into the via,operation 1240 of exposing, by the light guide, a portion of thephotoresist layer to light, thereby resulting in an exposed portion ofthe photoresist layer and an unexposed portion of the photoresist layer,an operation of 1250 of removing a portion of the photoresist layer, andan operation 1260 of plating an area of the via, where the photoresisthas been removed, with a metal, thereby resulting in a portion of thevia plated with metal and a portion of the via not plated with metal.

It will be understood that when an element is described as being“connected,” “deposited on,” or “coupled” to or with another element, itcan be directly connected or coupled to the other element or, instead,one or more intervening elements may be present.

The descriptions of the various embodiments of the present disclosurehave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

What is claimed is:
 1. A process comprising: providing a via in a basematerial in a direction perpendicular to a plane of the base material;applying a photoresist layer to an interior surface of the via;inserting a light guide into the via; and exposing, by the light guide,a portion of the photoresist layer to light, thereby resulting in anexposed portion of the photoresist layer and an unexposed portion of thephotoresist layer; removing a portion of the photoresist layer.
 2. Theprocess of claim 1, wherein a portion of an outer surface of the lightguide is masked.
 3. The process of claim 1, wherein the photoresistlayer is a positive tone photoresist material.
 4. The process of claim3, wherein the removing comprises removing the exposed portion of thephotoresist layer.
 5. The process of claim 1 wherein the removingcomprises washing the via with a photoresist developer.
 6. The processof claim 1, wherein the photoresist layer is a negative tone photoresistmaterial.
 7. The process of claim 6, wherein the removing comprisesremoving the unexposed portion of the photoresist layer.
 8. A processcomprising: providing a via in a base material, comprising at least twocopper lines and at least one insulator layer separating the at leasttwo copper lines, in a direction perpendicular to a plane of the basematerial, wherein the via intersects the at least two copper lines;applying a photoresist layer to an interior surface of the via;inserting a light guide into the via, wherein a portion of an outersurface of the light guide is masked; exposing, via the light guide, aportion of the photoresist layer to light, thereby resulting in anexposed portion of the photoresist layer and an unexposed portion of thephotoresist layer; and removing a portion of the photoresist layer. 9.The process of claim 8, wherein the masked portion of the light guidehas two or more masked regions separated by one or more unmaskedregions.
 10. The process of claim 8, wherein the photoresist layer is apositive tone photoresist material.
 11. The process of claim 10, whereinthe removing comprises removing the exposed portion of the photoresistlayer.
 12. The process of claim 8 wherein the removing comprises washingthe via with a photoresist developer.
 13. The process of claim 8,wherein the photoresist layer is a negative tone photoresist material.14. The process of claim 13, wherein the removing comprises removing theunexposed portion of the photoresist layer.
 15. A process comprising:providing a via in a base material, comprising at least two copper linesand at least one insulator layer separating the at least two copperlines, in a direction perpendicular to a plane of the base material,wherein the via intersects the at least two copper lines; applying aphotoresist layer to an interior surface of the via; inserting a lightguide into the via; exposing, via the light guide, a portion of thephotoresist layer to light, thereby resulting in an exposed portion ofthe photoresist layer and an unexposed portion of the photoresist layer;and removing a portion of the photoresist layer.
 16. The process ofclaim 15, wherein a portion of an outer surface of the light guide ismasked.
 17. The process of claim 15, wherein the photoresist layer is apositive tone photoresist material.
 18. The process of claim 17, whereinthe removing comprises removing the exposed portion of the photoresistlayer.
 19. The process of claim 15 wherein the removing compriseswashing the via with a photoresist developer.
 20. The process of claim15, wherein the photoresist layer is a negative tone photoresistmaterial.